> Geoffrey Hausheer
>>> but
>> he'll ask for some more information and a sample to figure out the
>> problem. I know he fixed quite a few bugs for me and others while 0.19
>> was still in SVN.
>>> Me too, while it was just a test app. I haven't had time to play
with it or run my "kill mpg" clip through it yet. I was looking pretty
good awhile back.
> Right, and that's the most important part. One of the primary reasons
> Geoffrey created the new lossless transcoder in Myth 0.19 was to allow
> simple commercial clipping without introducing A/V sync errors, since
> other available MPEG-2 tools did not properly handle issues in the
> PVR-x50 recordings.
> It's even more subtle than that. There's a few more
things going on than clipping commercials without A/V sync. The problem
with most of the other tools is that the ivtv cards change the *relative*
A and V sync offset throughtout a stream every once in awhile (generally
due to bad captures from tape, noisy signal, etc). That breaks most other
utils. AIUI, the lossless adjusts the offsets *everywhere* in the stream
to be a constant value... not just at the commercial cuts.
Another issue is of course the commerical cutting and what happens
if the sync changes inside a chunk that's cut. Also, it's
frame-accurate... so if you cut on a non-keyframe, it will convert
non-keyframes in the original GOP to keyframes in the output... thus
frame-accurate editing.
> So, basically, what the OP heard about cutting MPEG-2 applies to other
> tools, but Myth's lossless transcoder was created because of the
> problems those other tools had, so you shouldn't experience any A/V sync
> issues when using it.
> ... and had been a significant deficiency in MythTV since I
started playing with it 2 1/2 years ago. Lossless cutting/cleaning was
the only significant technical hurdle to decent archiving, and DVD
burning. With that in place, DVD authoring becomes simple (since the 99%
of the other linux MPEG processing tools won't barf on the streams now).
-Cory
--
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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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